JP3329293B2 - Material testing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a material testing machine,
More specifically, the present invention relates to a material testing machine capable of automatically determining an accurate break point of a test piece in a tensile test.

[0002]

2. Description of the Related Art In a conventional material testing machine, there is known a material testing machine having a function of automatically detecting a break point of a test piece when a tensile test is performed on the test piece. In this type of material testing machine, instantaneous detection that the instantaneous detection data of the load acting on the test piece shows a sudden decrease is stored, and the detected data is stored as break point data, or It is configured to output and automatically stop the data sampling and loading mechanism.

[0003]

By the way, the conventional material testing machine provided with the function of automatically detecting the break point as described above,
In a tensile test of a certain material, as shown in FIG. 4, the load value acting on the test piece gradually increases after the test is started, and the load value rapidly decreases when the test piece breaks. Whenever the digital conversion data of the load detection value by a load cell or the like is sampled, a sudden decrease in the load value is captured in real time in comparison with the data sampled so far, and the sudden Data indicating a decrease is detected as break point data.

According to such a conventional data processing method for detecting a break point, since the load reduction speed at the time of breakage of a test piece is generally fast, a slight detection delay involves a large error in the result of detection of a break point. Cause. In order to prevent such an error from occurring, it is necessary to increase the detection sensitivity of the load reduction, in other words, to set so as to detect a very small decrease in the load value. In some cases, a change in load data during a test in which a piece does not break is erroneously detected as a break point. Therefore, it is extremely difficult for a conventional material testing machine having such a break point detecting function to detect a break point accurately without erroneous detection.

[0005] Further, in the conventional material testing machine having the function of automatically detecting a break point as described above, as shown in FIG. 5, a test for a material which does not exhibit the above-mentioned sudden decrease in load at the break point is performed. In this case, automatic detection of a break point cannot be made to function. In this case, a method is adopted in which the data sampling and the stop of the load mechanism are performed, for example, when the load sampling data reaches a value close to 0. Therefore, the data corresponding to the true break point is the data sampling data. Sampling is performed at a time when the vehicle goes up a certain degree or more from the stop time, and it is left to a measurer to determine which load data is determined as a break point.

The present invention has been made in view of such circumstances, and there is no danger of erroneous detection even when testing a material having a fast load reduction rate at the time of breakage of a test piece. Its main purpose is to provide a material testing machine that can obtain data.

Another object of the present invention is to show a sharp decrease in load at the time of breakage, which could not be exhibited by a conventional material testing machine having a function of automatically detecting a breakage point. It is an object of the present invention to provide a material testing machine capable of obtaining break point data even when there is no material.

[0008] In order to achieve the above purpose, the material of the present invention
The testing machine is a material testing machine having a load mechanism for applying a load to a test piece and a load detecting means for detecting a load applied to the test piece by the loading mechanism every moment. A storage means for storing data every moment, and a break detection means for detecting that the test piece has been broken, and after detecting the break, from time series data of the load stored in the storage means, The peak value is searched backward from the data corresponding to the break detection time, and the peak load value is determined as the break point data .
(1) Break point determination means, and after the detection of a break, write in the storage means
When a break is detected from the time series data of the remembered load
Going up from the data corresponding to the point,
Search for the maximum value within the search range
A second break point determining means for determining as break point data,
Selectively operating the first and second break point determining means;
It is characterized by having a selection means .

[0009]

Here, in the present invention, as the fracture detecting means for detecting that the test piece has fractured, means for detecting a sudden decrease in the load detection value to detect the fracture, Any known means can be adopted, such as a means for detecting that the breakage has been reached near 0, and a means for detecting breakage. Is not used as the breaking point data.

According to the present invention , the load value sharply decreases upon breaking.
Testing of materials that do not show a sharp drop in load value at break
Testing of both materials
To select a break point determining means that is more suitable for the material
Is always trying to determine the break point accurately.
You. In testing of materials whose load value decreases sharply at break
In the past , a conventional material testing machine with a function of automatically detecting a break point captured in real time the point at which the load value during the test turned from a gradual increase to a sharp decrease, and used the load value at that point as the break point. On the other hand, in the present invention, the first breaking point is determined.
By selecting the means, it is separately detected that the test piece has been broken, and after that detection, the time data is sampled from the load data stored as time-series data in the storage means. By detecting the peak value, the erroneous detection of the break point and the detection delay can be eliminated, and the above-mentioned main object can be achieved .

That is, the load detection data during the test is stored in the storage means as time-series data every moment, and after the breakage of the test piece is detected by the breakage detection means, the time-series data of the load in the storage means is stored. From inside, the peak value is searched from the new data side to the old data. The peak value of the load obtained in this way always indicates an accurate break point regardless of the load reduction rate at the time of rupture, even if the rate of decrease of the load is fast, and the load fluctuates during the test. become.

Further , the load value shows a sudden change at the time of fracture.
Conventionally, in a test of a material having no break point, the measurer appropriately determines the breaking point from the test results such as a load-strain curve after the test.
By selecting, when the detection method of the break by the break detection means is constant, from the time of the break detection, the maximum load value within a predetermined search range going backward in time is taken as the break point In addition, by setting the search range empirically according to the judgment of the conventional measurer in accordance with the characteristics of the material, data close to the true break point can be obtained as break point data. Such a material whose load value does not show a sharp decrease at the time of such a fracture is known from the beginning of the test, or it is known from the second and subsequent tests of the same material even if it is unknown. such by selectively operating the second break determining means when testing materials, Ri Do enables automatic determination of breaking point data for almost all materials, the other purposes mentioned above
It can also be achieved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an embodiment of the present invention, and is a diagram showing both a schematic diagram showing a mechanical configuration and a block diagram showing an electrical configuration.

In this example, the mechanical structure of the tester main body 1 is known, and both ends of the crosshead 13 are supported on left and right screw rods 12a and 12b provided on a table 11 via nuts. The crosshead 13 is configured to move up and down by rotating and driving the screws 12a and 12b by a driving mechanism 14 disposed below the table 11. The lower surface of the crosshead 13 and the table 1
On the lower surface of 1, upper and lower grippers 15 a and 15 b are respectively arranged to face each other, and the test piece W is gripped at both ends by these grippers 15 a and 15 b, and by raising the crosshead 13 in this state. A tensile load is applied to the test piece W.

The upper grip 15a is provided with the crosshead 13
The load applied to the test piece W is detected by the load cell 16. An extensometer (not shown) is attached to the test piece W, and the elongation of the test piece during the test is measured.

The driving mechanism 14 of the screw rods 12a and 12b is controlled by a control signal from the control device 20, and the outputs of the load cell 16 and the extensometer are output at predetermined minute intervals of, for example, several milliseconds or tens of milliseconds, respectively. And is sampled by the data processing device 21 every moment. The data processing device 21 has a built-in storage device 21a such as a RAM for storing these load data and elongation data every moment, and also includes two types of measurement and
A keyboard 2 for selecting one of the control programs or setting a search range or the like to be described later;
2 and a printer 23 for outputting a test result.

The data processor 21 automatically detects the breakage of the test piece W according to the following program, and determines the break point of the test piece W after detecting the breakage. The momentary load data and the elongation data sampled by the data processing device 21 are output to the printer 23 as a load-elongation curve.
As a result, the break point data determined by the data processing device 21 is printed.

FIGS. 2 and 3 are flowcharts respectively showing the main parts of the contents of the two types of measurement / control programs written in the data processing device 21. Hereinafter, the present invention will be described with reference to these drawings. The operation of the embodiment will be described.

When testing a material whose load shows a sharp decrease at break, the measurement and control program of FIG. 2 is selected. In this program, when a test start command is given, the drive mechanism 14 starts driving and raises the crosshead 13, and at the same time, load data and elongation data are sampled every moment, and the data are sequentially stored in the storage device 21a in the order of sampling. Will be stored inside. Further, each time one load data is sampled, the sampled data is compared with the load data stored so far, and it is determined whether or not the load data has sharply decreased. When it is determined that the load data has sharply decreased, the drive mechanism 14 is stopped immediately after the test piece W is determined to be broken, and sampling of the load data and elongation data is stopped. Further, the time-series data of the load stored in the storage device 21a is read out, and the peak value of the load is retrieved by going up from the latest load data sampled at the time of detection of the break. Then, this peak value is printed on the printer 23 as break point data.

According to the method of determining the break point in this program, after the test piece W breaks, the final peak value is obtained from the time series data of the load, which is sampled and stored every moment until the break occurs. Can be obtained as break point data, so that data corresponding to the true break point illustrated in FIG. 4 can always be obtained accurately regardless of the load reduction rate at the time of break. Moreover, in this program, the capture of the sudden decrease in the load for detecting the breakage of the test piece W is not for the purpose of identifying the break point, but for the drive mechanism 1.
4 to stop the data sampling and to start the search for the break point using the data in the storage device 21a. Therefore, strict capture is not required as a particularly high sensitivity. There is no risk of erroneous detection.

On the other hand, when testing a material whose load does not show a sharp decrease at break, the measurement and control program of FIG. 3 is selected. When this program is selected, a range in which the load data is searched backward after the break is detected is set in advance by the keyboard 22. In this program, similarly to the above-described program, when a test start command is given, the drive mechanism 14 starts driving to raise the crosshead 13, and at the same time, load data and elongation data are sampled every moment. Each data is sequentially stored in the storage device 21a in the order of sampling. Further, the sampled load data is compared with a preset threshold value near 0, and when the load data falls below the threshold value, it is determined that the test piece W has broken and the drive mechanism 14 is immediately activated. Stop and stop sampling data. Further, the load data stored in the storage device 21a is read out, and the maximum value of the load within the search range set backward is searched from the latest load data sampled at the time of detection of the break. . Then, this maximum value is printed on the printer 23 as break point data.

According to the method of determining a break point in this program, a break point which could only be manually determined conventionally can be automatically determined by appropriately setting a search range in accordance with the characteristics of a material. . That is, when the load data stops sampling of the load data at the time when below a certain threshold, the true break exists where the climbed substantially constant range by temporally reverse from its last load data . This range is determined by the characteristics of the material. Therefore, if the search range of the load data is optimally set empirically in accordance with the characteristics of the material, the break point can be approximated to the true break point illustrated in FIG. Data can be automatically determined.

[0024]

As described above, according to the present invention, at the time of breaking
1st and 2nd breaks depending on how the load value decreases in
Point determination means can be selected, and the load value decreases sharply at break
When testing less material, select the first break point determination means.
By selecting, after the test piece actually breaks, from the time series data of the load momentarily stored in the storage device, to search for the peak value going up in time to determine the value as the breaking point Unlike the conventional automatic break point detection method that captures a sudden decrease in load data by real-time processing, there is no possibility that an error due to a detection time delay is included, and there is no possibility that a break point is erroneously detected.

Further , the load value does not decrease sharply at the time of breaking.
When testing materials, select the second stage determination method.
And by, after the specimen has actually broken, because it determines the value to find the maximum value within the set search range as a break, of automatically determining the breaking point by the conventional apparatus Even for a material that could not be obtained, a break point almost close to the true break point can be automatically detected.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, and is a diagram showing both a schematic diagram showing a mechanical configuration and a block diagram showing an electrical configuration.

FIG. 2 shows a main part of the contents of a measurement / control program written in the data processing device according to the embodiment of the present invention, which is selected when testing a material whose load value shows a sharp decrease at break. It is a flowchart.

FIG. 3 shows a main part of the contents of a measurement / control program written in the data processing device according to the embodiment of the present invention, which is selected when testing a material whose load value does not show a sharp decrease at breakage. It is a flowchart shown.

FIG. 4 is a graph showing an example of a temporal change of load data obtained at the time of a tensile test of a material whose load value shows a sharp decrease at break.

FIG. 5 is a graph showing an example of a temporal change of load data obtained at the time of a tensile test of a material whose load value does not show a sharp decrease at break.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tester main body 11 Table 12a, 12b Screw rod 13 Cross head 14 Drive mechanism 15a, 15b Gripping tool 16 Load cell 20 Control device 21 Data processing device 21a Storage device 22 Keyboard 23 Printer

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Claims (1)

(57) [Claims] 1. A material testing machine comprising: a load mechanism for applying a load to a test piece; and load detecting means for detecting a load applied to the test piece by the load mechanism every moment. A storage means for storing the load data every moment, and a break detection means for detecting that the test piece has been broken, and after detecting the break, from among the time series data of the load stored in the storage means. , Search for the peak value from the data corresponding to the break detection time, and determine the peak load value as the break point data
A first break point determining means, and, after the break is detected, the storage means
Break detection from time series data of stored loads
Going back from the data corresponding to the time,
Search for the maximum value within the search range
Second break point determining means for determining a value as break point data
Selectively operates the first and second break point determining means.
A material testing machine comprising a selecting means for causing the material to be tested.